58.010 Colias croceus (Clouded Yellow)
ws: m52-58mm, f 54-62mm; migrant May-Oct; clovers (Trifolium spp), lucerne (Medicago sativa); commonest in coastal counties of south England but fairly common throughout England and Wales, less so in Scotland. Early migrants breed after arrival (and can produce up to 3 generations in GB). Peak numbers occur Jul-Sep when the bulk of continental migrants arrive.
ID: Yellow with a broad black band along the upperside termen of both wings. The only other common yellow British butterfly is male Gonepteryx rhamni (Brimstone) which has a distinctively pointed forewing apex and hindwing termen and lacks any black marks on the forewing upperside. The female C.croceus has a pale variant (form helice) which is very similar to C.hyale (Pale Clouded Yellow) and C.alfacariensis (Berger's Clouded Yellow). In C.croceus the dark border of the hindwing extends as a band of black from the mid-costa around the apex, along the termen almost to the tornus; in C.hyale/alfacariensis the black marks are much less extensive, occurring as more discrete blotches at the ends of the veins around the hindwing apex.
Page published 02/05/2014